Secondary galvanic cells and electrodes of such cells



P. sALlsBuRY-Rowswsu. 2,609,407'

Sept. 2, 1952 y SECONDARY GALvANIc cms AND ELEcTRoDEs oF sucH cms Filed may 2s, 194s f1 'Sheets-Sheet 1 l NVE NTOR M sAusBuRY-RowswELL EYS Z-Fy' www,

ATTOR v Sept. 2, 1952 P. sALlsBuRY-RowswEl- L 2,509,407

SECONDARY CALVANIC CELLs AND ELECTRoDEs oE suCH CELLs mea May ze, 194e 4 Sheets-Sheet 2 MLN nw @E j/a 'i N m m Illa Nvx-:NTCR 4d? PELHAM SAUSBURY-RowswELL EY gf 5* A ORNEYS Sept. 2. 1952 P. sALlsBuRY-RowswELL 2,609,407

SECONDARY GALVANIC CELLS AND ELECTRODES OF SUCH CELLS Filed may 2e, 1948 54 'Nm/m 52@ C f6 O O ffdf/ UUR/ jip; f4

Hg if INVENTOR PELHAM SALISBURY- ROM/5W ELL BY '@5- W l ATroRN evs l4 sheets-sheet s Sept. 2, 1952 P. sALlsBURY-RowswELl. v f 2,609,407

SECNDARY GALVANIC CELLS AND ELECTRODES OF SUCH CELLS Filed May 26, V1948 mus-sheet 4 mmmm INVENTQR' fau-IAM sAusuRY-Rowswl-:LL

i' BY ff4-w- ATTORNEYS Patented Sept. 2, 1952 SECONDARY GLVANIC CELLS ANI)A ELEC- 'I'RODES 0F SUCH CELLSv Pelham Salisbury-Rowswell, LondomfEngland Application May 26, 1948, Serial 'No.f29-,323 InGreat Britain November 22, 1947 6 Claims. A 1

invention relates to electric accumulator-s .orfstorage'batteries Afor lexample, of the leadlead peroxide type andiron-.or nickel or cadmium types.

ll-hev electrodes .of such batteries are subject .todeterioration` due A11o-'growth or expansion of the active material and its shedding lduring. use and buckling -dueto i111 use and various proposals have *beel'l'made for :reducing or avoiding such defects.- Thus retainers for the vactive material have beenemployed which in the ca-se'of pencil or .rod'form electrodes either single, or in the ormof ai plate comprising a plurality of parallel pencilsor rods, `were `each provided with .asleeve which permitted .access of electrolyte to the .active materialV therein but made of material inert to the electrolyte and action which takes place when the. battery is in .use or being charged'.

Thefpri-mary-objectzof the invention .isto providean improved .retaining-.sleeve which is simple to manufacture .and which. when in use will .readilyexpand with vgrowth or expansion of Athe active material.

.A further-object of. the invention is to provide .electric accumulators or storage batteries `emhodyingsuch electrodes whereby their more effieient operation `is attained.

A still further object is to provide a method of and .apparatus for manufacture of the improved sleeves.

The invention comprises an `electrode for secondary cells or accumulatore comprising active material in contact with a conductor, the active material being lretained by a sleeve of plastic material` inert .to the electrolyte, helically formed Aand transversely perforate or imperforate where .by electrolyte canl obtain access to the active .material through thel space between adjacent edges of the helical turnsof the -sleeveor through the perforations or both, andthe sleeve .can Aex pand 4the action of Iexpansion or growth Aof the active material.

It vis essential that the plastic lmaterial employed be `acid. resistant and aV non-conductor of electricity and one example of synthetic plasticmaterial is methyl methacrylate. Other suitable--thermo-plastic materials are hard, natural, or synthetic rubber, styrenes, polystyrene-and sleeves. i

Amethyl methacrylates in unplasticised state .and which are porous. Further the character of the Asleeve must be such .aste-provide for deformationunder .the v`action yof grow-th. or expansion ofthe active material and recovery fremde- 'formation if. shrinkage Vor contraction of the activematerial takes-place after growth whereby Y thesleeve. willl :always firmly engage Vthe active -materia`l'.

Y i v`Referringq.now to .the accompanying drawings; l Y ,'Figure iis; a., sectional velevation` oiga pencil scribing such manufacture lit may be" n 2 -orrod .form `electrode according to .the invention, the gure also illustrating in dotted lines lhow 'a further lpencil or pencils may beassembled together to provide a multi-pencil plate or electrode. Y

Figure la is an elevation `Vshowing'am-sliV ht modification. l Y' Figures 2, 3, 4, 5 and 6 and 7, 8.8c'andl8b -arejeach -a sectional-'elevation of -a modiedom Aof electrode. y j...

Y Figure 9 is a sectional elevation of av complete secondary battery accord-ing to the-invention. Figure 9a is a diagrammatic representationof a four pencil positive plate and a ve'pencil negative lplate :in which the pencils areaccording to Figure 8a. H

Fig-ure 10 is a sectional elevation suitablev for hand torches.r l V Figure 11 is a diagrammatic plan' View the .arrangement of positive and negative. plates-according to the invention. y 2

.Figures 12, 13 and `14 are. resp.ectively"`a's'ec tional side elevation, vpart sectional side elevation and plan of apparatus vfor making theretairng sleeves, and A p Figure 15 is a sectional elevation of arnold .form of apparatus for making.V the fr.

ffa. battery Y Y YFigures 16 .and 17 are respectively a ele'.- vation v(andlend View tof .a further modifieljirm Vof manufacture of a. retaining sleeve, .the "v vvvs being diagrammatic. Y l

l Figure 18 vis 2a sectional elevatiorifof van' tive lelectrode in which a further modi'iied crrnfb retaining sleeve is-il1ustrated,. andy l.

.Figure 19 isa sectional .elevation of a positive `electrode A.showing .another modification of the .retaining sleeve. 4,

g Figure la is ra fportio'n oi"V a thermo-'plastic retaining sleeve! which vv can befformed `byfheli- .cally winding a heated strip .of thermo?. resin, methyl metha'crylate, 'for example, `Q a .rod orman'drel of cylindrical or yother o'ss .section so that .the edges of the coils `,o'r"c`on volutions are' slightly spacedV .apart an hen allowing the .sleeve .to `.c.oo l.`,`The v'stripfloefore being Wound` onto the'mandrel .may loe pierced ,while heated so .as to provide .a plurality of small `passages la transversely through r tl'ffe" si'I""1'J. After Ythe SIeeVeJLhas cooled.tofnormalfft'emp ,ature it is .slid o'fthe. mandrelpr rod. .an then ready. for'. as'senilo'lyv with other vmanufacturean electr`o'de.Y ,Beforeg'howe 1I the sleeve. .has uthe physical attribute of pression)springfinasinuch as it can' be' xpanded .axiallyby holdingneendfstationaryaridp lll g hererpnniiigtthends-,simu

e. a 1ra-vivi @naar i initial condition. If therefore active paste be held as by friction or other means within the sleeve and the paste expands or grows, the sleeve will expand to allow for said growth and contract when the paste contracts. Further if the ends of the sleeve are each in a plane at right angles to the axis and the sleeve ts between two fixed members which abut the ends of the sleeve, expansion or growth of active paste lling the interior cf the sleeve will be confined to radial expansion and the helical sleeve will be expanded radially so that its diameter will increase but it will resume its former diameter if the paste subsequently contracts.

The transverse passages should not exceed tti of van inch in diameter and they provide for increased access of electrolyte to the active mate- Arial.

Referring now to Figure l which showsa positive electrode for a lead-lead peroxide storage battery or accumulator, there is provided a rod of lead 2 depending from a terminal lug 3. Surrounding the rod intermediate its ends and in contact therewith is a cylindrical body 4 of active material which is surrounded by an imperforate sleeve 5 of thermoplastic material, as hereinbefore described, the adjacent edges of the helical convolutions being slightly spaced apart to permit electrolyte to gain access to the paste. The upper end of the sleeve is covered by a ring 6 of the same thermoplastic material as the sleeve and the ring is united with the upper end of the sleeve by applying solvent to one or both the members and pressing them together until they are integrally united.

' A ring of the same thermoplastic material as the sleeve is also united with the lower end thereof by the employment of a solvent and the lower end portion of the lead rod, which extends through the openings in the rings, is bent so as to underlie the lower ring. The rings slidably fit the rod and when an electrode, according to the foregoing description, is in use in a battery and growth or expansion of the active paste occurs, the sleeve 'will alsoexpand axially, the upper ring under action of such expansion sliding upwardly on the rod. If subsequent shrinkage or contraction of the paste occurs, the helical sleeve will resume lits initial unstressed condition, the upper ring returning to its initial position relatively tothe rod. This figure also shows in dotted lines how another electrode element may be assembled with the electrode above described to provide a two or if required a three or more multipencil electrode or plate, the lead rods of both or all the rods being secured to a common lead bar, as shown in dotted lines, by burning, the bar being provided with a suitable terminal lug (not shown).

The active material may lbe formed into a briquette having a Acentral passage for the rod, `the hriquette being inserted into the sleeve before one of the rings is secured in place. The rod can then be slid through the central passage in the active material and the openings in the rings until the forward end of the rod projects below y the lower ring, Figure 1. Finally the projecting portion of the rod is bent over at'right angles to 'supportl on the rod the enclosure formed by the in Asitu during charging of a batteryjby filling the f .cylindrical space between the rod and the sleeve `Awith pure red leadpowder or paste containing such material, it being understood that such ll- 4 ing will be effected before one of the rings is secured in place.

In Figure 2 a lead conducting rod 'I isprovided which has burned thereto a leaddisc 8, which disc has burned thereto and depending therefrom a perforated tube of thin lead 9, the lower end of which has burned thereto a disc of lead 8a. This structure carries retaining means comprising as hereinbefore described, a sleeve IU closed at the lower end by a disc II of thermoplastic material and has at the other end a ring I2 secured thereto through which the rod 1 extends and on which the ring can slide. Te space between the sleeve and the lead tube and the interior of the latter are filled with active material.

A further modified form of pencil electrode is shown in Figure 3, and in this form of the invention the active material is contained in a perforated lead tube I3 closed at its upper end by a ring of lead burned to the conducting rod I4. The tube I3 substantially ts the interior of a retaining sleeve I5 provided with top and bottom rings I6 and I1 secured to the sleeve. The interior of the lead tube is lled with active material I8. As shown another lead tube Illa may extend downwardly from the rod I4 which may or may not be filled with active material.

In Figure 4 there is shown a further form in which the lower end of a lead'conducting rod I9 projects into active material 20 within a retaining sleeve having end rings as described with reference to Figure 1, the rod having depending therefrom and burned thereto a perforated tube of lead 2| which may or may not be lled with active paste. In the latter case electrolyte lls and can circulate in the lead tube and gain access to the paste through the perforations in the latter.

Figure 5 shows a further modified form in which a retaining sleeve 22 surrounds a body of active material 23 in contact with a central rod of lead 24, the latter having secured thereto, as lby burning, lead discs 25 which cover the upper and lower ends of the sleeve but are not secured to the latter.

As will be appreciated in this formof the invention, expansion of the active paste will cause expansion of the sleeve radially of the rod as the sleeve has its ends prevented from movement axially by the discs 25.

Referring now to Figure 6, a positive pencil electrode is shown, having inner and outer spaced retaining sleeves 26, 21, the upper and lower ends of the annular space thus alforded between the sleeves being closed by rings 28, 29. A tubular member 28a of perforated lead is located within Vthe outer retaining sleeve and is spaced from the latter, a conducting rod 38 projecting downwardly into said space through a notch in the upper ring 28 and being burned to the tubular member 28a. Active paste lls the space between the inner sleeve and the lead tube and it will be appreciated that electrolyte can gain access to the active material exteriorly and interiorly thereof.

Figure 7 shows how a strip of thermo-plastic material can be wound to provide spaced inner and outer retaining sleeves 3I, 32 and a bottom closure 33 for the annular space between them.

'The annular space is filled Withthe active paste and a lead rod or other member may project downwardly through a cover ring secured to the upper ends of the sleeves, into the active paste.

.The cover ring 33a is of thermo-plastic material and has on its underside annular grooves 34, 35

into which the upper portions of the sleevesextendglthe sleeves and cover ring '-being integrated lduringmanufactureiofthe `pencil bythefemp'loyment of a solventfovhicnris '.introduoedrintofthe grooves, vthe sleeves f-being ithen-.lappliedto the vcover ring with their -upper ends .in the vgrooves V`It will Y1b'e-fseen fthat the bottom elosurefis 'formed `Eloy a tpluralityfef concentric windings .of theistrip andi it Will-.also be seen .that thefdepth 'of vvthe str-ip ymaterial formingithesirmer 'sleeve andthe concentric Windingsiisless .thanthat forming the outer sleeve. In formingthesleeves 4:tltie'lstrip k'is .nrstzpreformed accordingly, f thenarrower :por-tion poing :thenhelcally .mound .on .to Ia-`nietal mandrel,leaving`I sucient .of iits'len'gth -for the ywinding ofithe concentric .-ccnvoltiens. .The -latter are then wound .and faftnbularLmetal mandrel is slid `on to"the;=sleeve1already iorrned and the wwider. portion of -Ithestrip =is thenwound .on to the tubular f Imandrel. The Y:ma.nd1.els Y :are

. '11s/ithdrawny from' the .sleeves .after :the .latter have icooledzto anormal temperature .and fthesleevesiare then assembled With the fcoverirnga.

It will `bezunderstood .that :when growth ;or ex- =pansionio1the :paste takes place'tvvillact axially of'the concentric 'winding-s zand extend :both ythe inner and-outersleeves.

1j..[nV Figure :8A .amulti-,pencil .positive .electrode orplate` is'..-shown-.com:prising1 a. plurality soi .retaining .sleeves 133e which are .alternately wound :in 'the oppositesense,4 the upper ends of 'the Y sleeves being united by :solvent :to arbar 3:6fwh'ich has A.openings .13.7 therethrough .coaxial )with the sleeves. :Thelower .ends of `the .sleevesrare similarly: unitedftca .bar :alsoihaving .openings .39

Acoaxial With'ethe sleeves, -anda coverband!) '.un-

providedrJ-ith .cpenings is secured tbyisolventito 'the iba-.1238. "Eachfsleevejhas.zalead rod extendsing downwardly thereintqIthe rods extending through the oDeningsSl substantiallytoethe lower portions of'thefslee'ves.

The rods are provided with outwardly projecting collars,torngues'xor .spil es,;andactire material -ils the spaces betweenrtherodsuaind thesleeves. :Thesproieeting .col-lars, tongues .or 4spikes Pholdvthe 'active material inipcsitionrcn'zthefrods. Theirods tare-.each E` burned .at v.their l.upper lfen'ds :.t-o; afzlead havingza' terminal` lug :ftnot'fshoivnlV rintegral therevriftli. 'The openings iin '.the` upper I thermo- 'plastic bar are such-thatsaid :bar .carrslidetliere- 'onziigrowth .or .expansion .of the act-ive .material willzeaet 'to more Ithe .npperzalnd `lower in opposizteidirections. .l A;.suitableorm .oflea'd:rodiiZaior'longipencils isisliown ingmte 18h and can 'befrnadelby .pressing a circular :rodto .form connected .ovalp'late porizions ..allternately in planes at'riglrtfangles Itoeachother.' Y

:Figure '18o .alsofshoxvs Va helical sleeveSaSa-sseml:bled with'the'rod, and. active materiali!! between the 'latter .fa-nd: the sleeve. The interior lrdiameter .of the `sleeve is .only fslightly .greater than fthe 4Width of the pla-tes vand with .such an `arrangement the rod serves to maintanrfthe sleevefrcm substantial Ilexnre transverse to its .or axial zmisalignment. .with the 'red `.during charging. iAno'ther uorm of :pencil electrode 'fis-shown Figure-adhering :a Vcentral'pcoruiueting :rod .ib .of .lead provided 'with aflange' 2b biirnt' on `to :the :rod-or cast integrally therewith.

thermoplastic` retaining. sleeve .13a4 :snrrounds :the fcyli'ndricalj body; .of active material :4alandLhas1a lowerfclosurezdisc 51': of thermoplastic Vmaterialv which-nits thei sinterior :of the eieevecand'"isaintegrated-therewith iby `the :em-

.'plotmentr tof. .-.ai solvent. The' .centralfpotion f fof :the discihasadepressionf'a circulariincross ssee- Y locatelithe douter .end y.of 'the .trod lwhen the j.parts :of thefvelectrode fare :assembled as lherlei-Irafterfrv vuferredlito.. 1 The 4top of the sleeve-is closed by z-.aringrfla-fcf thermo-plastic material whichfits in gche .sleeveiand isfintegrated therewith bylthe :employmentfof -.a fsolvent. Ih--e.rng1 'la fts ithe 4ex'tc'arliorof"the lead rottend zitszunderside bears on the iflangelrb. A 'ileadiconducting member '-.'a having-.arc'entral Vopening l.Winch `Vlits the proj ecting-portionsof :the rod Ib `is burned .tomheltter 'and-has v-an 4upwardly projecting Vtermir'ial,Slug 'lmet-shown). The conducting member 18a ibears at'itsvunderside von the tring vla. will beseen trom the ldotted :portioncfv Eigure 8a two or more fof the pencilfelectrodes may depend 'from ".a `sing-le lead conducting member .or fbar 48001110111113- i-vitle la' positive plate, .but as the .pencilsarenct connected together, except at theirupper .endsiby tthek conducting Einem-ber 8a. .each retainingsleeve vcan :expand .under actionV ofexpansion .or growth of the :active .material :therein independently'f .of the other retaining -sleeve or sleeves :of .the plate. ITo :assemble the :parts .of .ai penciLfaccordingito iigurefa, .the :disc 5b is fsecured,z.as'above referred to, vin theilowerend of .thesleeve 13a. 'Therad' la :havingithereon below the vflangezb .a briquette-tof active material, v.or a body .'ofspastefof slightly less diameter lthan Athe interior of l the 1 Vsleeve :'3 a, -is-.then slid' into the :sleeve ifrornthe :upper end :thereof .until .ajpcrtion .9b-ofthe -rod IbJiWhi-ch projects tbeyond thellower end of the briquette :or lpas-te .entersthe depression 16a. The `ring 1a ris then :threaded .cnf-.to the portionuof Iizherrod which projects .above-.the langethereof and .the .ring'is secured .to .the upperfportion .ofthe'sleeve .by'so'lvent the conducting member "Ba threaded .on to rod `l orsoV thatitzbearsfon the 'ring V'Iza themernloerfa. -is then `burned .to .the rod. Whether .a briquette of .active 7material for paste is'femployed'it lmay 'be 'united withf'thewrod prior to` assembly, Withlth-e retainingsleeve, ias .byv providing 4collars ier projections ifromthefirod which .enter the .briquettematerial or 'paste-'dur- -ingfmoulding of the'material .or paste-"onthecrod vIn keither case the active .material lwillbeizorile more. firmly united withitherod during :charging and .thus thefweight of 'the vactive material `will 'be borne entirely 'by-vtfhe Vrodisofthabnormally'-the sleeve, Which'is also carried 'by ithefrodfwill-fbe in unstressed condition. However,.1as lWilllie-'aprpreciatedfif the active materialaexpands or grows when the electrode ,use thesleeve willexterrd longitudinally. v

Figure .9.afshows diagrammatically ,in plan' .view a four pencil positive plate 10a in which lthe 'pencils are. according tofFigure 8a, depend fromla commonoondueting bar'a Which-leprovided withfia'terminalflug `(notfshovv'n) 4The negative plate'comprises five pencils each. according to'Figure 8.a andzdepending from ;a=common icon:- Aductingbar `I'Ia 'also providedwith af'terminail lug (notshown). The plateszare snpportecl so as todependzfintoan electrolyte container tand "are lheldin theire'lative positions zshownin the 'gixre `by any suitaia'lemeans. Aswill'beiappreciated'the retaining *sleeves 'of the negative "pencilsvwill connefthespong'y leadftl'ierein and Willi'alsofex- 'pandrnnderiaction of :expansion of `the lead.'

he secondary :battery .or accumulator'V shown finfilsligure 'i9fl'ias psitiveandnegative electrodes 3411', 35a and an 'acidcontainer 36a 'Whiehisoif any suitable acid resisting material, for example,

moulded ebonte or thermosetting plastic. The positive electrode comprises a retaining sleeve 36h united at its upper and lower ends respectively to a ring 31a and a disc 38a both of thermoplastic material and secured to the sleeve. A lead rod 38h projects downwardly through the opening in the ring 31ul and into contact with active material 39a filling the interior of the sleeve, the rod being provided with collars or other projections which prevent relative movement between the paste and the rod. The upper end of the rod has a post provided with a terminal 40a. .The negative electrode comprises perforated lead sheeting alla. bent to provide an annular space to contain active material and the upper part of the sheeting has burned thereto a post provided with a terminal 42. The negative electrode surrounds the positive electrode in spaced relation thereto and the electrodes are supported in the container with their lower ends above the bottom thereof.

Figure'l() shows a secondary battery according to the invention suitable for use in hand torches 'and comprises an outer case t3 of acid resisting material, for example, oi ebonite or thermoplastic synthetic resin, having tightly tting 41 which at its other end is secured to a metal negative contact terminal 53 for engaging a spring in the torch case, and projecting from and secured to the bottom wall of the casing. VThe positive electrode may be according to Figure l except that the upper end of the rod t9 projects through an opening in the tcp wall of the case and has formed at the upper end a disc providing a positive contact terminal. The casing is filled with electrolyte comprising a, gel preferably isinglass containing dilute sulphuric acid.

In Figure'll the multi-pencil positive electrode or plate has the pencils arranged in two parallel laterally spaced rows 56 and 5l, the negative electrode or plate 52 being of perforated sheet lead and of boX form, and provided with a negative terminal lug 53. The upper lead bars 55, 55 of the rows of pencils are connected by a bridge piece of lead 56 burned to the bars and having a positive terminal 51.

In manufacture the pencils are filled with pure red lead paste and the negative box electrode with litharge which are respectivelyccnverted into PbOz and sponging lead during charging.

VThe walls of the box which face the rows of positive pencils may be formed so as to have vertical cylindrical depressions alternating with vertical projections so that the side-faces' of the negative electrode considered in plan' view conwith mien and @unen slots 5s, su for the passage into and from the oven of a strip 6l of thermoplastic `synthetic resin. Within the oven are a pair oi `upper and lower rollers 62, 63 which are ofthe vsame diameter and may be smooth surfaces rifV the strip is not to be perforated. The rollers Yare rotatablyv mounted and geared together to rotate at the same speed and the upper roller is spring urged into contact with the lower roller and is adjustable to determine the pressure of contact.

The lower roller has a plurality of circular rows of sharp. pointed pins 64 the diameter of the body of each of which is substantially j/ei of an inch and the upper roller has a plurality of continuous peripheral grooves 65, one for each row of spikes, the grooves being of slightly greater width than the diameter of the pins so that there is no contact of the spikes with the sides of the grooves, and the latter being of a depth so that the pointed ends of the` spikes do not contact with the bottoms of the grooves.

Secured to a bracket below the outletV slot are a pair of bearings 66, 61 for a mandrel 58 of steel or hard rubber, the mandrel having a spindle one portion 69 of which is screwthreaded for engagement by a half nut 1U pivoted at 1| tothe adjacent side of the oven and which with the half bearing 12 forms the bearing for that end of the spindle. The other end of the spindle is adapted to rotate and slide in the other bearing 61. The rollers and the mandrel may be rotated by a motor and as will be understood rotation of the Vmandrel will cause by virtue of the screw and half nut, traverse of the mandrel axially. When the machine is to operate the oven is heated to a temperature sufflcient to soften the thermo-plastic synthetic resin to enable it to be pierced by the spikes during passage between the rollers, and its subsequent winding into helical form.

One end of a strip of thermo-plastic synthetic resin of suicient length for producing a sleeve of the desired axial length, is then passed through the slot 59 into the oven and into the bight between the rollers 62, 63 which perforate the heater strip and feed itv out of the outlet slot 60 to'a suicient distance to enable the end portion to be attached in any suitable manner to one end of the adjacent end of the mandrel. The feeding by the rollers is then temporarily interrupted and the end portion of the strip attached to the mandrel while the latter is also stationary. The mandrel and rollers are then rotated and the strip is helically wound on to the mandrel. The half nut is' then disengaged from the screwed portion of the spindle and the mandrel removedfrom its bearings whereupon the sleeve is slid axially ofi the mandrel. If the end portions of the strip have not been, prior to operation thereon, cut so that the ends of the sleeve are in planes at right angles tothe sleeve axis the ends of the sleeve are cut olf and the sleeve is then ready for embodiment in an electrode.

lIn ligure15,v 66 is an electrically heated oven having therein rotatably mounted thereon a roller or mandrel 61 having a screw threaded shaft 68 which is engaged by an internally screw threaded half nut 69 which is pivoted to a member (not shown) Xed within the oven,v so' that it can be moved into and out of engagement with the shaft. The other end of the roller projects through an opening 1U in the adjacent oven wall 1|,"which wall is preferably offheatr insulating material, -into a 'cooling chamber 12.1" Above the roller 61 and adjacent to the Wall 1| is a piercing roller 13 having radially projecting pointed spikes which are arranged in a helical row and of a pitch corresponding to the screw of the shaft 68. The roller 13 is spring urged towards the roller 61 so that a heated strip of thermo-plastic will be pierced as the rollers rotate. 'I'he rollers 61 and 13 are geared together to rotate at the same peripheral speed and may be driven through the gearing by a motor. The strip of thermoplastic material enters the oven through a slot (not shown) in the wall 1,4 rearward of the rollers 61 and 13 and which is on the same level as the bight between the rollers 61 and 13.

With the foregoing arrangement a strip of thermo-plastic material of a length suitable to provide a sleeve for an electrode to be manufactured is projected through the slot so that its inner end is held in the bight between the rollers 61 and 13. When the part of the strip in the oven has become softened by the heat the rollers are set in rotation and the strip is helically wound on the roller 61 and at the same time pierced by the spikes. Axial traverse of the roller 13 by virtue of the screw and half nut, causes movement thereof through the opening into the cooling chamber where the sleeve becomes set so avoiding possibility of flow of the thermoplastic after it has been wound and pierced, it being understood that such provision in particular avoids the holes produced by the piercing from becoming lled.

Figures 16 and 17 illustrate manufacture of retaining sleeves of hard rubber for positive pencil electrodes. An extruded or moulded tube 14 of such material is taken and slid on to a mandrel 15 of the same exterior diameter as the interior diameter of the tube 14. 'Ihe mandrel 15 is mounted between lathe centres carried by al suitable support or base having provision for rotating the mandrel in the direction of the arrow, Figure 17, and traversing it axially in the direction of the arrow, Figure 16. The sleeve is cut into the form of a helix by a rotary circular saw or knife 16 arranged at a suitable angle and which is rapidly rotated in the direction of the arrow, Figure 17, during rotation and traverse of the mandrel so as to cut through the sleeve to the periphery of the mandrel so that the side wall of the sleeve is changed to helical form. If desired the tube 14 may be of moulded or extruded thermo-plastic synthetic resin or thermo-setting resin and cut to helical form according to Figures 16 and 17.

When the tube has been so cut it is removed from the mandrel and may be assembled with other parts required to produce a pencil electrode as hereinbefore described.

A further method of manufacture of retaining sleeves, Figure 18, may comprise dipping vcylindrical cores in a dispersion or solution of rubber or thermoor thermo-setting plastic and then cutting the side wall as described with reference to Figures 16 and 17, to form it into a helix. The

cores may be dipped a plurality of times in the..

dispersion or solution in order to build up their wall to the desired thickness.

It is to -be understood that the invention is not conlned to lead-lead peroxide storage batteries `as it may ebe applied to alkaline storage cells in which the conducting members are of nickelplated steel and the active material nickel peroxide mixed with graphite for a positive electrode,

and finely divided iron and graphite for the negative electrode.

Further the retaining "sleeves may be of other thermo-plastics may be employed.

Finally the retaining sleeves are not confined to cylindrical formation as the helical turns may be of square, rectangular, oval, hexagonal or other conguration when viewed in the direction of the axis of the sleeve.

I claim:

1. An electrode for secondary or storage batc teries comprising a conducting member, active material in contact therewith and a preformed helically Wound self-sustaining sleeve containing said active material, said helical sleeve being composedV of a resilient ribbon-like material which is inert to the electrolyte and to electrolytic action, the helices being spaced apart to permit passage of electrolyte therebetween so as to ycontact the active material, said sleeve supporting said active material in a resilient relationship.

2. An electrode as claimed in claim 1 wherein the sleeve is composed of thermo-plastic material and wherein the conduc-ting member is a rod extending from the exterior of the sleeve axially therethrough, said rod being secured to one end of said sleeve, and wherein the active material is of cylindrical form and is disposed between the rod and the interior of the sleeve.

3. An electrode as claimed in claim 2 wherein the other end of the sleeve has secured thereto a cover of thermo-plastic material, the inner face of which ts the adjacent end face of the active material.

4. Retaining means -for the active material of pencil electrodes of storage batteries comprising a self-sustaining tubular member of electrical insulating material inert to electrolyte, said member consisting of end portions and a resilient ribbon-like strip connecting the end portions and helically wound about the tube axis with the edges of the convolutions being spa-ced apart Wherebyjelectrolyte can gain access to the interior of the sleeve.

5. Retaining means for the active material of pencil electrodes of storage batteries comprising a self-sustaining tubular member of electrical insulating material inert to electrolyte, said member consisting of end portions and a plurality of resilient ribbon-like strips each 'connected at its ends to the end Iportions, each strip being helically wound about the tube axis, with the edges of each strip being continguous and parallel to adjacent strips.

6. Retaining means as claimed in claim 5 wherein the tubular member is of rubber and the strips are integrally united with the end portions.

PELHAM SALISBURYROWSWELL.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Welsh Dec. 

